Participants will undergo three exercise sessions on separate consecutive mornings after fasting overnight. Before each test, patients (not healthy volunteers) will take either an additional morning dose of hydrocortisone or a placebo (a lookalike pill with no active ingredient). Before each test a thin catheter (plastic tube) will be placed into an arm vein through a needle. A numbing cream can be applied to make the needle stick hurt less. Blood will be drawn through this intravenous (IV) line before, during and after the exercise tests. The first test is a maximal exercise test to determine the individual's maximum exercise fitness capacity. The second two and third tests are a standardized exercise tests. Before the two standardized tests, patients (not healthy volunteers) will take either an additional morning dose of hydrocortisone or a placebo (a lookalike pill with no active ingredient). All tests are done on a stationary bicycle.